The word telefon probably generally wouldn't be used to refer to a cell phone or a mobile, right? Only an old-fashioned landline-style phone?
Tangentially, I had a fun time explaining to my 5-year-old nephew recently what a 'phone booth' was, and why there used to be a need for them. He just couldn't fathom the concept of phones actually being permanently attached to walls. I would have loved to have seen what was going on in his imagination during that conversation. :-)